摘要:
砂质辫状河内部不同级次的构型模式,特别是心滩坝及其内部夹层的构型特征尤为重要,直接控制了油田开发中后期剩余油富集与分布。采取现代地质调查与地下地质解剖相结合的思路,以渤海海域P油田为例,分别从辫流带、心滩坝及心滩坝内部夹层三个级次,探讨了砂质辫状河构型特征及其对剩余油分布规律的影响。结果表明砂质辫状河道具有三种充填样式,且以砂质充填为主,心滩坝与辫状河道呈"宽坝窄河道"的分布样式;坝内落淤层具有穹窿式和水平式两种分布样式。此外,从5级至3级构型单元逐步细分,通过三种识别标志划分单一辫流带,平均宽厚比约178;心滩坝辫状河道宽度与心滩坝宽度比约为1:3.8,心滩坝宽度与长度比约为1:2.2;心滩坝内部单期落淤层近水平分布,多期之间互相平行,一般2~4个。不同级次储层构型要素对剩余油分布的控制存在差异性。对于辫流带级次,层间隔层直接控制剩余油分布;心滩坝级次泥质半充填河道底部砂体连通,侧翼上部水淹程度较低,剩余油富集;受落淤层和物性界面的影响,心滩坝内部剩余油主要呈"分段式"富集在落淤层下方垂积体的顶部和水驱较弱的边部。该成果在油田老区综合调整方案和新区开发方案设计上得到了应用,也在调整井部署,尤其是水平井挖潜剩余油等方面,提供了地质依据。
Abstract:
The architecture of braided river, especially the muddy intercalation, plays a key role in the enhancement of remaining oil. Based on the outcrop, modern sediments and underground reservoir, taken P oilfield as an example, the different level of the internal architecture elements are studied in order to obtain a qualitative and quantitative distribution pattern of the heterogeneity character of the sandy braided river reservoir. Also, the architecture characterization technique for underground braided river reservoir is studied in this work. Based on the proposed distribution pattern and the related characterization techniques, the different control of architecture element to the distribution of remaining oil is analyzed:① the sandy braided rivers have three filling types, dominated by sandy fillings. The distribution styles of channel bars and braided rivers display "wide bar-narrow channel". The sludge beds within channel bars show two distribution styles as dome-like and horizon-like. ② architectures from 5 to 3 hierarchies are characterized successively. Based on three identification marks, single braded belts are characterized with width of 800~1200 m, thickness of 3~8 m and average width/thickness ratio about 178. Channel bars are characterized by principles of thickness-controlled, scale-constraint and multidimensional interaction. The width ratio of braided rivers and channel bars is about 1:3.8, and width/length ratio of channel bars is about 1:2.2. Single periodic sludge bed within channel bars are horizontally distributed and different periodic sludge beds are parallel with each other. The distribution range of sludge beds from bottom up decreases from bar head to bar tail. The quantity of sludge beds within channel bars are generally low (about 2~4). ③ reservoir architectures of different hierarchies exert different controls on the distribution of remaining oil. The interlayers control the remaining oil directly in the hierarchy of braided river belts. In the hierarchy of channel bars, the sandbodies are connected at the bottom of muddy semi-filling channels, resulting in relatively poor water flooding degree and enriched remaining oil in the upper part. Influenced by sludge beds and petrophysical boundaries, the remaining oil within in channel bars is mainly distributed as "segment-like" at the top of aggraded bodies under the sludge beds and the margin part with poor water flooding. This research has been applied in the optimization of water injection and deployment of wells of oilfields.
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